Greetings, Devil Dog! Welcome to the Call of Duty Forums. It looks like you're looking forward to Call of Duty: Modern Warfare 4, but haven't created an account yet. Why not take a minute to 
Activision and Infinity Ward introduced a new system to deploy with Call of Duty: Modern Warfare 4. That system is called "Server Culling" and the system is designed to combat wallhacks. The anti-cheat system will block a cheat system from seeing the other side of the wall, before they even use the wallhack. The way Infinity Ward describes it, is when you get to the wall, the server hides your player character from the client from ever being able to see you in real time.
View: https://www.youtube.com/watch?v=nYN3MPRuznU
